1. Field of the Invention
This invention relates to a dual steering system for off-highway vehicles containing both a primary steering system for normal operation and a secondary steering system for emergency operation. More particularly, this invention relates to a totally divided steering system from the steering cylinders outward such that, despite a malfunction of any single component in one part of the system, adequate control can be maintained by the unaffected parts of the system.
2. Description of the Prior Art
Vehicular steering in large, off-highway vehicles is normally accomplished through a hydraulic steering system connected to the front wheels. Failure of the hydraulic pump or failure of the engine to operate can affect the steering. An obvious safety problem can arise from the loss of steering in these large vehicles. Hydraulic steering systems of this type are dependent upon operation of the vehicle engine for power to operate the system. The steering may also be disrupted by hydraulic failure due to broken hydraulic or fittings or leaks in the system.
Therefore, it is a principal object and purpose of this invention to provide a fully redundant steering system including a primary steering system for control of steering in normal operation and a secondary system capable of operating despite the total failure of any of the major components of the primary system. It is also a principal object and purpose of this invention to utilize a pair of steering cylinders common to both the primary and secondary system and to have either system provide steering control despite loss or malfunction of one cylinder. It is a further object and purpose to utilize the concept of proportional flow dividers to compensate for the difference in area at the opposite ends of a hydraulic cylinder.